This invention relates to a process for production of acrolein, and in particular to a novel and improved process for production of acrolein by gas-phase catalytic oxidation of propylene in which a catalyst of improved composition is utilized.
In production of unsaturated aldehydes by the gas-phase catalytic oxidation of olefins, the use of especially will-prepared catalysts and the selection of most appropriate conditions for the desired reaction are generally importance in order to maintain high conversion of the starting olefins and to keep high selectivity to the desired unsaturated aldehydes and unsaturated carboxylic acids.
There have been already proposed numerous catalysts in order to accomplish these purposes. To give some examples of the catalysts of the class containing molydenum and bismuth in combination, for instance, there are Mo-Bi-P catalysts (as disclosed in Japanese Patent Publication No. 3563/61), Mo-Bi-Fe-P catalysts (Japanese Patent Publication No. 7522/67). In spite of their own advantages, each seems, so far as we know to have some disadvantages in one or more of such points as one-pass yield, selectivity, and durability of the catalyst.
The unsaturated aldehydes produced by the use of such catalysts are often converted to unsaturated carboxylic acids by the ensuing step of oxidation. In this case, the olefin conversion must be kept as high as possible from the economical and industrial point of view. This object has so far been accomplished, wherever the prior catalysts have been used, by such usual procedures as elevating the reaction temperature or increasing their contact time. These procedures, however, accompany a noticeably lowered selectivity of to the unsaturated aldehydes.